I want to backup my virtual machines (all Debian) with a cronjob. As the backups per machine can be pretty huge I only want to backup the system with its configuration itself (leaving out the directory where users mess around), which can be done with the exclude-dir-parameter.

I'm planning to run the cronjob once a week. But I really only want to backup the machine if something has changed in the system configuration or new packages have been installed. Is there a way to detect such changes in a virtual machine before running vzdump?

I've just started with git though - it is not a problem to have that many files versioned?
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acmeMar 7 '11 at 9:00

With git you can version Gigabytes with 10,000s of files - all operations (even merging) will complete in seconds. Here are some measurements that I did biocluster.ucr.edu/~alevchuk/git-test.txt - I predict that Git will scale to 100s of Gigabytes and 1,000,000s of files and the run times for all git operations will stay under 5 minutes on a decent storage (directly attached).
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Aleksandr LevchukMar 7 '11 at 15:58